OROPHARYNGEAL OR GASTRIC COLONIZATION AND NOSOCOMIAL PNEUMONIA IN ADULT INTENSIVE-CARE UNIT PATIENTS - A PROSPECTIVE-STUDY BASED ON GENOMICDNA ANALYSIS

Colonization of the digestive tract has been supposed to be the source of many hospital-acquired infections, especially nosocomial pneumonia . To assess the relationship between oropharyngeal and gastric coloniz ation and subsequent occurrence of nosocomial pneumonia, we prospectiv ely studied 86 ventilated, intensive care unit (ICU) patients. Orophar yngeal or gastric colonizations were detected and quantified on admiss ion and twice weekly during ICU stay. When nosocomial pneumonia was su spected on clinical grounds (new chest X-ray infiltrate and purulent t racheal secretions), diagnosis was assessed on fiberoptic bronchoscopy with quantitative cultures of a protected specimen brush sampling and /or a plugged telescoping catheter sampling yielding greater than or e qual to 10(3) cfu/ml of at least one microorganism. Bacterial strains responsible for colonization and infection (Acinetobacter baumannii, P seudomonas aeruginosa, Enterobacteriaceae, and Staphylococcus aureus) were compared using pulsed-field electrophoresis. A total of 31 cases (36%) of pneumonia were diagnosed. Oropharyngeal colonization, detecte d either on admission or from subsequent samples, was a predominant fa ctor of nosocomial pneumonia as compared with gastric colonization. Fo r instance, oropharyngeal colonization with A. baumannii yielded a 7.4 5-fold estimated increased risk of pneumonia as compared with patients not yet or not identically colonized (p = 0.0004). DNA genomic analys is demonstrated that an identical strain was isolated from oropharynge al or gastric samples and bronchial samples in all but three cases of pneumonia, due to S. aureus. These findings provide better knowledge o f the pathophysiology of nosocomial pneumonia in mechanically ventilat ed patients.